Droppable container



March 12, 1957 Filed Dec. 21, 1953 c. P. BENDER 2,784,755

DROPPABLE CONTAINER 2 Sheets-Sheet 1 INVENTOR Charles RBender BY aw J16ATTORNEY March 12, 1957 r c. P. BENDER4 2,784,755

DROPPABLE CONTAINER Filed Dec. 21, 1955 2 Sheets-Sheet 2 INVENTORCharles P. Bender BY 51/21/1 4 r%c5 ATTORNEYS United. States PatentDROPPABLE CONTAINER Charles I. Bender, Wabash, Ind., assignor to TheGeneral Tire and Rubber Company, Akron, Ohio, 21 corporation of OhioApplication December 21, 1953, Serial No. 399,212

9 Claims. (Cl. 150-.5)

This present invention relates to a rubber drop tank which is filledwith liquid or freely flowing fine particles and dropped from aircraftto ground receivers. It particularly relates to a rubber drop tank thatis provided with a stabilizing flap to slow down and control itsfreefalling aerodynamic characteristics.

In the copending application of Paul O. Pfeiffer, Serial No. 262,116filed December 17, 1951 and assigned to the same assignee as the subjectinvention, the process of filling rubber drop tanks with fluid or freelyflowing fine particles and dropping them from aircraft to groundreceivers is described. In accordance with this process, a rubber droptank can be filled with a fluid such as gasoline and dropped to theground from heights of around two hundred feet to one thousand feet ormore.

The object of this invention is to provide a container for use inaccordance with this process with superior aerodynamic characteristicsand particularly a container that falls flat and right side up.

Other objects and advantages will become apparent from the followingdetailed description and the accompanying drawings illustrating thisinvention in which like numerals relate to like parts.

Figure 1 is a top plan view on a reduced scale of a droppable containerconstructed in accordance with this invention;

Fig. 2 is a cross-sectional view taken along line 22 of Fig. 1;

Fig. 3 is a fragmentary cross-sectional view taken along line 33 of Fig.1 and on a larger scale showing the stabilizing flap of this invention;

Fig. 4 is a front elevationalview showing the droppable container ofFigs. 1 to 3 filled with liquid and showing in dot-dash lines how theslits in the stabilizing flap may be used as handles;

Fig. 5 is an enlarged fragmentary cross-sectional view taken along line5---5 of Fig. 1 showing the closure means and filling handles for thecontainer;

Fig. 6 is a fragmentary circular cross-sectional view taken along are6-6 of Fig. 1 indicating by dot-dash lines the method of attaching thefilling handle to the container; i

Fig. 7 is a front vertical cross-sectional view on a re duced scaleshowing a modified form of container constructed in accordance with thisinvention; and

Fig. 8 is a front elevation showing the approximate free-falling shapeof the container of Fig. 7 when it is filled with liquid.

Containers constructed in accordance with this invention are filled withfiowable materials such as gasoline,

water, dry powders, or freely flowing fine particles such on the groundcollect the containers and empty them. It

is contemplated that this process may be used in both 2 military andcivilian work to supply persons behind enemy positions or in isolatedlocations.

The container is a relatively thin-walled, hollow body with fillingmeans such as a plug generally in the center of the top portion. In thefilled condition and resting on a horizontal support, the horizontalwidth is preferably at least five times the height and the shape of thecontainer is generally spheroidal or ellipsoidal with the bottom portionof blunter profile than the top portion. It should be oblate ordepressed at the vertical poles. Thus the preferable shape of thecontainer when filled and resting on a horizontal support is generallythat of an oblate ellipsoid of revolution. Other shapes such as a pearshape or the like are also contemplated by this invention. The containershape should also be rounded and curving and have no sharp corners orstress concen tration points and should preferably be symmetrical aboutits vertical axis.

The containers themselves are subject to extreme forces and must beconstructed in accordance with definite limitations. In the first place,it is assumed that in the great majority of drops, the containers willreach their maximum or terminal velocity as they fall to and beforereaching the ground so that they will normally strike the ground attheir terminal velocity. To minimize the impact forces, therefore, Idesign my container to have a minimum terminal velocity and to have asmuch air resistance as can be incorporated therein Without being undulycomplex, costly, or cumbersome. I try to design the containers withterminal velocities below 300 feet/sec. and preferably around 100 feet/sec. or below The container is shaped so that spinning and whirling inthe air is minimized and so that it will not otherwise fall in anerratic fashion. I have found that a skirt or flap around the maximumdiameter of the container greatly assists in overcoming spinning andwhirling during free fall.

One form of container or bag constructed in accordance with the subjectinvention is illustrated in Figs. 16. This container 1 comprises acircular top sheet or disc 2 and bottom sheet or disc 3 vulcanizedtogether at lapped-over, seam portion 4. As shown in Fig. 3, the edge 7of sheet 3 laps over the edge 6 of sheet 2 and they are vulcanized orcemented together at seam portion 4. The inner side of each sheet 2 and3 may have a thin layer of aromatic resistant rubber-like material suchas HYCAR or THIOKAL or the like so that gasoline can be transportedtherein wtihout injury to the bag walls. The inner lining should be moreflexible than the bag walls proper so that the lining does not absorbshock forces or become separated from the walls. It is contemplated thatan outsized, loose lining of cellophane or polyvinylchloride sheet orthe like could be inserted within the bag to protect special goods suchas food products. A reinforcing disc 8 is preferably vulcanized to thecentral portion of the bottom sheet to reinforce and strengthen it. Themeansfor filling the container comprises a plug 9 which is screwed intoa socket or flange 11. Around the top of the socket is a washer orgasket 12 to prevent leakage. The socket is built into the top portionof the bag with top and bottom circular rubber pieces 13 and 14respectively as shown in Fig. 5. The: plug is provided with a centraldepression 16 provided with ears 17 so that a tool or bar can beinserted into the depression to open the plug. Both the plug and socketare preferably made of a polyester resin reinforced with glass fibers.

The unfilled container is preferably provided with a circumferentialhump portion 10 in sheet 2 around the top of the container adjacent thefiller means as shown in Fig. 2. This portion extends completely aroundthe top of the container. It provides extra stretchable material for thetop portion of the container so that it can stretch evenly with thebottom portion, or in other words, so that the top and bottom portionsof the container have approximately the same amount of stretchablematerial. This is preferable because the flange around the plug isunstretchable and reduces the efiective stretch of thetop portion ofthis container. When the container is filled, the hump is preferablysubstantially eliminated.

In order to facilitate handling the container and particularly in orderto facilitate filling the container, a rubber ring member 18 isvulcanized to the container to form handle portions 19 and 21 (Fig. l).The ring member preferably has a fabric facing 22 on both sides andcomprises two rings of rubber 23 and 24. As shown in Fig. 6, the bottomrubber ring 24 is split, folded back and'vulcanized to the container andthe exposed portion of the top ring is also vulcanized to the'container. The remainder of the ring forms right and left handleportions 19 and 21 previously noted.

I also provide a stabilizing skirt or circumferential flap 26 around thecentral circumference of the container and extending appreciably beyondit to give the container aerodynamic stability and to decrease itsterminal velocity. This flap 26 is generally attached or vulcanized tothe container at or near the maximum circumference of the container ornear the juncture or seam porion 4 of the discs 2 and 3. It ispreferably made from a ring of rubber-like material which is vulcanizedor cemented to the container as shown in Fig. 3. It should have a widthor diameter so as to extend beyond the margin of the container wall insubstantially a horizontal direction of from around one eighth to onehalf the radius of the bottom portion of the container as assembled, or,in other words, from seam {1 to the vertical axis of the container. Thusfor a bottom sheet radius of approximately 12. inches, the flap shouldpreferably extend 3 inches beyond the seam. It should be attached to thecontainer body in the vicinity of the maximum diameter and should extendan appreciable distance in a horizontal direction beyond the side of thebody or beyond maximum circumference of the container body. In Fig. 3 itis shown vulcanized to the container at seam portion 4.

. Opposite sides of the skirt are provided with handle portions 27 and28 consisting of fabric pieces 29 and 31 vulcanized over slots 32 in theskirt. The fabric over the slots is then slit as at 33 to form handlesor hand grips s'uitabl'e for lifting and handling the container as isillustrated in Fig. 4.

. i The container 1 when filled and resting on a horizontal support as in Fig. 4 assumes substantially the shape of an oblate ellipsoid ofrevolution substantially symmetrical about a vertical axis in which thediscs 2 and 3 are bowed or bulged outwardly. When the container iscollapsed, 'the disc s are substantially fiatwise against one anotherand the upper disc 2 has a slightly greater diamete'i tha nthe otherdisc 3.

Fig'l'7 shows a modified form of container constructed inaccordance'with my invention. Container 35 comprises a circular topsheet or disc 36 and a circular bottom sheet 37 of smaller diameter thanthe 'top sheet joined to the top sheet along seam 38. If desired, seam38 may be'reinforced as with stitching or rivets A portion of the topsheet extends beyond seam 38 to form flap portion 39 functioningsimilarly to flap 26 on container 1. It should extend beyond seam 38 insubstantially a horizontal direction a distance of from one eighth up toone-half the radius of bottom sheet 37 and preferably a distance ofaround one-quarter of this distance.

The plug 40, socket 41, and filling handle ring 42 form a closure andfilling means for the container similar to that of container 1.Likewise, flap portion 39 is provided with cloth reinforced handleportions 43 and 44 similar to those of container 1.

It is, of course, desirable to have the filled container fall and landin its normal," upright position so as not to injure the valve or plugfor emptying and filling the container, to minimize terminal velocity,and to minimize the landing shock and stresses on the container. Inorder to aid in accomplishing this result, I shape that portion of thecontainer opposite from the filling valve and near the maximumhorizontal diameter so that the container when filled and freely fallingprovides increasing air resistance as it is tilted earthward from thehorizontal. That is, the lower part of the container is shaped so that,when the axis of the container is tipped from the vertical, the airresistance of the higher portion of the container will decrease and theair resistance of the lower portion will increase. A self-rightingeffect is thus obtained similar to that caused by the dihedral angle inairplane wings, the stabilizing skirt greatly assisting in this action.The outer portions of the cross-sectional curve of my container may bemade to be fiat, concave, or only slightly convex to obtain the desiredself-righting effect. w

The container of Figs. 7 and 8 is provided with excellent stabilizingmeans, Fig. 8 showing the approximate shape of this container when it isfilled and freely falling so that the action of the stabilizing flap 39is apparent. It will be noted from Fig. 8 that the bottom sheet 37 has aconvex outer surface of revolution that decreases in curvature andextends generally in a radial direction adjacent its margin so that, incross section, there is a sharp interior angle formed by the top sheet36 and the marginal portion of the bottom sheet 37. In other words, theradially outer'portion of the bottom sheet 37 is generally tangent tothe top sheet 36 and its flap portion 39.

The material used in making my container should be tough, abrasionresistant, and flexible. Suitable materials are natural and syntheticrubbers and rubber-like ma terial's." The required physicalcharacteristics of the material must be adapted to the goods transportedin the container taking into account their specific gravity, sol ventactionfcompatibility, and sanitation requirements. A suitable materialmust satisfy a combination of several requirements in as even a balanceas possible. The material has to'be quite flexible'in order to give anddistort on landing and "thereby absorb and dissipate the landing forces.At the same time, it should have sufiicient modulus so that a filled'container retains shape on the ground and the walls do not collapse. Thebag should preferably be sufliciently rigid in the filled state so thatit can be readily stacked and moved about. It should also havesuflicient modulus sothat the shape of the container during free fall isone providing maximum air resistance and is not distorted to "astreamline teardrop shape. At the same time, bags constructed inaccordance with this invention should have no unstretchable continuousreinforcing material in the wallsbecause this unduly limits the wallelongation and flexibility. The material 'finally should have toughnessand abrasion resistance to stand handling and resist ground hazards suchas trees, rocksQand stubble.

The material for this container can be any high abrasion resistant,nervy, flexible rubber or rubber-like material such as natural rubber,'butadiene-styrene rubbers, butadiene-acrylonitrile rubbers, isobutylenerubbers, and other rubbery elastomeric materials. Minimum tensilestrength should be 1500 'p. s i. and preferably over 2500 p. s. i. andminimum elongation at break should be around 400. percent. The bag wallsection, regardless of thickness, ought to have a tensile strength orpull of 2090 p. s. i. or above at 500 percent elongation. Thus, if a lowmodulus material'is used, the wall should be relatively thi'ckandconversely, if a high modulus material is' used, the wall should be"relatively thin. A suitable container has a wall pull or tensilestrength of 4000 p. s. i. at 500 percent elongation. The material shouldbe compounded to provide high abrasion resistance and toughness. Arubberstock should pref,-

erably have 25 parts or more of a reinforcing carbon black or equivalentto provide toughness, hardness, abrasion resistance, and resistance tocutting. High quality tire tread stock satisfying the above notedphysical characteristics is suitable for use in my containers.

It is contemplated that bags constructed in accordance with the subjectinvention will have a capacity of five, ten, twenty-five, or even moregallons. Using the same stock, the bag wall thickness should beincreased when the bag is designed for heavy liquids such as waterinstead of lighter liquids such as gasoline.

It is understood that the invention disclosed can be constructed in anumber of ways within the scope of the appended claims and that it isnot to be limited to the embodiments herein described.

Having thus described my invention, what I claim is:

l. A droppable free-falling container for aerial delivery whichcomprises walls formed of two substantially circular rubber discs ofsubstantially the same diameter joined at their peripheries, said discshaving a minimum tensile strength of 2000 p. s. i. at 500 percentelongation and each being substantially fiat in the unstressed conditionand being disposed flatwise against one another when the container iscollapsed, a stabilizing flap comprising a ring of rubber-like materialjoined to said container adjacent the juncture of the two discs andextending in a substantially horizontal direction appreciably beyond theside of the container, said container when at rest on a flat supportingsurface and filled with liquid assuming substantially the shape of anoblate ellipsoid substantially symmetrical about a vertical axis withthe horizontal width at least five times the height in which the twodiscs are bowed outwardly and one disc includes a substantially circularflattened area of less diameter than the disc which is in contact withsuch supporting surface.

2. A container for aerial delivery of a freely-flowing material to theground from an air vehicle traveling at substantial altitude comprising:an extensible elastic rubber bag with a volumetric capacity of severalgallons having thin circular top and bottom walls joined at theirperipheries which walls may be extended several times their normaldiameter, the rubber of said walls containing at least about 25 parts ofa reinforcing carbon black and being capable of withstanding a tensionof at least about 2000 pounds per square inch when elongated fivehundred percent, said bag when completely filled with said material andresting on a flat horizontal surface having an axial height notsubstantially greater than about onefifth its diameter and when fallingfreely having a shape generally corresponding to that of an oblateellipsoid of revolution with a normally upright axis, and means forstabilizing said bag during its free fall so that said axis remainsupright during the fall to minimize the terminal velocity and is uprightwhen the bag strikes the ground, said stabilizing means comprising acircumferential flap of rubber-like material united with and extendingradially outwardly from the margin of said 'bag and having an averagewidth that is around one-eighth to one-half the radius of the lowerportion of the bag.

3. A container for aerial delivery of water, gasoline, or other liquidsto the ground from an air vehicle traveling at substantial altitudecomprising: an extensible elastic rubber bag with a volumetric capacityof at least about five gallons having thin circular top and bottomwalls, joined at their peripheries which are substantially free ofinextensible reinforcement and may be stretched several times theirnormal diameter, the rubber of said walls being capable of withstandinga tension of at least about 2000 pounds per square inch when elongated500 percent, said bag when completely filled with said material andresting on a fiat horizontal surface having an axial height notsubstantially greater than about one-fifth its diameter and when fallingfreely having a shape generally corresponding to that of an oblateellipsoid of revolution with a normally upright axis, and a stabilizingflap comprising a ring of rubber-like material united with saidcontainer adjacent the juncture of the top and bottom walls andextending radially outwardly from said juncture, said flap maintainingthe axis of the bag in an upright position during the free fall andincreasing the air resistance of the container so that the bag has aterminal velocity less than 300 feet per second.

4. A container as defined in claim 2 wherein a reinforcing disc isbonded to the interior face of said bottom wall at the central portionthereof and. wherein means is provided at the center of said top Wallfor insertion and removal of liquid.

5. A container as defined in claim 3 wherein said flap is integral withone of said walls.

6. A container according to claim 3 wherein the bottom wall decreases incurvature adjacent its margin.

7. A container as defined in claim 3 wherein the marginal portion of thebottom wall extends generally in the same direction as the flap.

8. A container as defined in claim 7 wherein said top wall and said flapare integrally uni-ted as a single sheet of elastic rubber, said bottomwall having a radially outwardly extending marginal portion parallel toand bonded to said sheet throughout its circumference.

9. A container for aerial delivery of Water, gasoline, or other liquidsto the ground from an air vehicle traveling at substantial altitudecomprising: an. extensible bag of elastic material having thin circulartop and bottom walls which may be stretched several times their normaldiameters, the bottom wall being joined at its periphery to the topwall, and means for stabilizing the bag during its free fall including aring of elastic material united with said bag adjacent the juncture ofthe 'top and bottom walls and extending radially outwardly from saidjuncture 'to provide a stabilizing flap, said means for stabilizing thebag maintaining the axis of the bag in an upright position during thefree fall and increasing the air resistance of the container so that thebag has a terminal velocity not substantially in excess of about onehundred feet per second.

References Cited in the file of this patent UNITED STATES PATENTS1,166,862 Smoot Ian. 4, 1916 1,340,236 Mochle May 18, 1920 1,754,776Stanley Apr. 15, 1930 1,834,978 Shapiro Dec. 8, 1931 2,343,512 Lobl Mar.7, 1944 2,430,905 Bradley Nov. 18, 1947 2,641,292 Quillinan June 9, 1953

